The present invention relates to the field of optical communication and optical data transfer. More specifically, this invention relates to optical switching of guided light waves from a first bank of waveguides that carry incoming optical signals to a second bank of waveguides that carry outgoing optical signals with the ability to DROP some optical data streams and to ADD others to the outgoing multiplexed stream composition.
This invention relates to the field of optical communication and optical data transfer. These fields are becoming of ever more importance in our networked world, with needs of ever faster communications.
There are several innovations already in this area. In U.S. Pat. No. 5,699,462 to Fouquet, et al., titled xe2x80x9cTotal internal reflection optical switches employing thermal activationxe2x80x9d incorporated herein by reference, in U.S. Pat. No. 5,960,131 to Fouquet, et al., titled xe2x80x9cSwitching element having an expanding waveguide corexe2x80x9d, and in U.S. Pat. No. 6,055,344 to Fouquet, et al., titled xe2x80x9cFabrication of a total internal reflection optical switch with vertical fluid fill-holesxe2x80x9d various aspects of the construction and operation of a guided wave, fluid activated, optical switch based on total internal reflection is described. But these patents do not teach the present invention.
An invention relating to the switching of guided light waves from a first bank of waveguides that carry incoming optical signals to a second bank of waveguides, with xe2x80x9conxe2x80x9d-xe2x80x9coffxe2x80x9d switches rather than routers, is reported by Shubin, I. et al, titled xe2x80x9cA guided wave optical switch controlled by a micro electro mechanical cantileverxe2x80x9d in LEOS 2000. (13th Annual Meeting. IEEE Lasers and Electro Optics Society 2000. Rio Grande, Puerto Rico Nov. 13-16, 2000, Conference Proceedings vol.1, P50-1). But this publication does not teach the present invention.
The present invention describes an optical switch, or router, which uses evanescent wave tunneling across a variable size physical gap. Electromagnetic wave tunneling becomes very efficient across a narrow tunneling gap discontinuity, while it is negligible for a wide tunneling gap discontinuity. In a medium in which optical losses are negligible, this means that in the case of a narrow gap optical energy is transmitted into the medium adjacent to the gap, while for a wide gap optical energy is reflected back into the incident medium. This is in fact the basis for the optical switch subject of this invention.
To make an evanescent wave tunneling switch practical it is necessary to judiciously add a number of thin films to both sides of the gap on the incident and adjacent media in the path of the propagating electromagnetic wave. The multilayer thin film structure on both sides of the gap constitutes tunneling gap engineering and its purpose is to alter the phase of the propagating light at the gap discontinuity so as to be able to exercise control over the magnitude of the gap for which efficient tunneling or propagation occurs as well as over the magnitude of the gap for which inefficient tunneling or reflection occurs. Tunneling gap engineering is discussed as are a number of means for actuating and controlling the gap width as it is changed from narrow to wide, and vice versa, in order to affect optical switching.
The construction and operation of an Mxc3x97N optical routing array being capable of directing light from any one of the M input ports to any one of the N output ports with additional ADD/DROP functions, using the invented optical switches, or routers, is also demonstrated. A waveguide crossing means is disclosed for the efficient operation of the optical arrays.